The development of data processing systems, computers and computer applications has transformed different processes into computerized processes. One example of such a process is modeling. Modeling means that a model is created from a product under design for describing the product to be constructed, the model containing at least information needed to illustrate the product. A product may comprise one or more articles. Computer applications typically apply predefined object types that are provided with values in connection with the modeling to create objects (models) of articles that exist or will exist (or at least are planned to exist) in the real world. Examples of these object types in the field of building modeling include beams, columns, plates and reinforcement. A product model may comprise in principle an unlimited amount of objects, some of the objects being similar ones, i.e. replaceable with each other. To facilitate manufacturing, or work at a construction site, for example, the objects or some of the objects undergo a process called numbering. During the numbering process, the objects are provided with “labels” so that objects having the same label are similar ones. A label identifies the object accurately enough. For example, four objects, each representing a column for a building, the columns differing from each other only on their location in the building, can be identified with one label. It is much easier in the construction site to take a column with the label amongst columns transferred to the construction site and erect the column compared to a situation when each column would have a unique identifier. However, if one of the columns has different outer dimensions, it must have a different label than the others, since it is not replaceable with the others. The evolvement of modeling to a multi-user modeling with shared data in a server, not only in real-time but also offline, creates challenges for the numbering, or to any corresponding grouping operation, especially if one target is to ensure that objects that are not replaceable with each other do not belong to the same group and have the same label, for example.